Complexes of polyelectrolyte gels with oppositely charged surfactants: Interaction with metal ions and metal nanoparticle formation

The interaction of polyelectrolyte gel/oppositely charged surfactant complexes with AgNO3 and H2PtCl6 was investigated. Three kinds of gel/surfactant complexes were studied: a complex of the anionic gel of poly(methacrylic acid) with the cationic surfactant cetylpyridinium chloride and complexes of the cationic gel of poly(diallyldimethylammonium chloride) with two anionic surfactants: sodium dodecyl sulfate and sodium dodecylbenzenesulfonate. After reduction of metal compounds by hydrazine-hydrate, sodium borohydride, or UV-irradiation, Pt and Ag metal particles embedded in the body of the hydrogel were formed. The degree of metal ion exchange was higher for the oppositely charged metal ion and the polyelectrolyte gel; i.e., Ag+ is strongly absorbed by the complex poly(methacrylic acid)/cationic surfactant, while PtCl62- ions are mainly consumed by the complex of poly(diallyldimethylammonium chloride) gel with anionic surfactants. Small-angle X-ray scattering data indicated different structural changes in the gel for the complex of an anionic gel with cationic surfactant and for complexes of cationic gel with anionic surfactants. The incorporation of the metal ions in the body of the hydrogel and the growth of metal nanoparticles was found to lead to the loss of order provided by surfactant aggregates if the distance between charged groups in the polyelectrolyte does not provide a strong hydrophobic interaction between surfactant molecules.